P0597 trouble!

**Andy86** · 06-02-2022, 07:51 PM

Hey everyone, long time lurker first time poster. I have been researching this for about a week now and can't seem to find anyone else who has had a similar thread. I bought a 2006 325i, automatic, recently that had a check engine light on, from a guy at work to use for commuting. I figured it was a simple fix but boy, I am having a time. Three codes were present in the pcm, one was thermostat stuck open, (can't remember the code for this one) P0597 (thermostat heater control circuit open), and P0440, EVAP emissions system. I figured they were all related to the bad thermostat, so I changed it, which got rid of the stuck open code, but the other two persist. So I have inspected the wiring harness as best I could and found a small bare spot in one of the two wires, which I fixed by cutting soldering, and heat shrinking the wire, but with no change. So I am stumped, I cleared the codes again, waited for them to trip again and looked at the freeze frame data, (hadn't started the car yet but the accessories were on) the ECT was 174.2° F. Ran the car for about 15 minutes at idle, cleared the codes again and looked at the freeze frame data again. ECT was still 174.2°F and fuel system 1&2 are showing the car is still running in closed loop. So I changed the coolant temp sensor, still same temp on freeze frame and closed loop fuel condition. I don't know where else to look as I can't find any wiring diagrams. Sorry for the long post, but any help is greatly appreciated. Thanks everyone!

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